Guinea Pig Manure. Organic Matter For Composting Or To Go Straight Into Bed For slow reaslise nutrients Qaste goes threw a screening process to give you only the most nutrient parts for gardening Guinea pig waste can be added directly to the garden without the worry of burning your tender plantings. This manure breaks down quickly and shares all the same nutrients as rabbit dung like nitrogen and phosphorus. Theres no need to compost beforehand. However, this is not to say that you cannot put it in the compost pile. In fact, many people actually prefer to toss it in the compost heap.